There has been extensively provided an optical disk device dedicated to reproduction, including a CD player or a video disk player employing an optical disk such as a digital audio disk or so-called compact disk or a video disk. There is also proposed an optical disk recording and/or reproducing apparatus in which data may be recorded and/or reproduced with the use of a rewritable opto-magnetic disk.
It is noted that, for optically reading the information recorded on the optical disk, an optical pickup head is extensively used in which the laser light is radiated on the recording surface of the optical disk to detect the light reflected from the recording surface. The disk dedicated to reproduction presents reflectivity on the recording surface different from that on the recording surface of the recordable disk, such that, in the case of the optical disk dedicated to reproduction, such as the compact disk, about 90% of the light is reflected by the aluminium reflecting surface applied to the recording surface, whereas, in the case of the rewritable opto-magnetic disk, about 10 to 20 percent of the light is reflected from the opto-magnetic recording layer, such as the TbFeCo layer.
For assuring compatibility with respect to the compact disk in the optical disk recording and/or reproducing apparatus employing a rewritable opto-magnetic disk, it is necessary to switch the gains of the tracking servo or focus servo employing the reproduction outputs obtained at the optical pickup head, or occasionally to switch the polarities of the error signals in dependence upon the kind of the optical disk which is in use, since the reflectivities on the recording surfaces of the disk dedicated to reproduction and the recordable disk are different from each other, as discussed hereinabove.
Thus the present invention is aimed to realize an optical disk recording and/or reproducing apparatus wherein the operation of the optical disk recording and/or reproducing apparatus is switched automatically in dependence upon the kind of the optical disk to enable both the disk dedicated to reproduction and the recordable disk to be reproduced, and provides an optical disk discriminating device which is adapted for discriminating the disk dedicated to reproduction and the recordable disk from each other.